McReynolds was born in Birmingham, Alabama. His NASCAR career began in 1975, and he worked his way through the sport's support roles before taking his first crew chief position in 1985. Over the next fifteen years he compiled 23 Cup Series victories, 21 poles, 122 top-five finishes, and 209 top-tens across 417 starts — statistics that earned him selection to the Copenhagen/Skoal All-Pro Team five consecutive years from 1991 to 1995.
His first Cup win came in 1988 at Watkins Glen International with driver Ricky Rudd.
McReynolds' career gained national prominence when he joined Robert Yates Racing in 1991 as crew chief of the No. 28 Ford, paired with driver Davey Allison. The partnership proved immediately successful: McReynolds and Allison won 11 races between 1991 and mid-1993, including back-to-back victories in the NASCAR All-Star Race in 1991 and 1992 and Allison's victory in the 1992 Daytona 500. The 1992 championship chase went to the final race, with Allison narrowly losing the title.
Allison died in July 1993 following a helicopter crash at Talladega Superspeedway. McReynolds transitioned to working with Ernie Irvan, who took over the No. 28 under controversial circumstances. Irvan won two of nine races in his abbreviated 1993 run and was a strong contender in 1994 before suffering life-threatening injuries in a practice crash at Michigan International Speedway. McReynolds had called Irvan in from the session but Irvan completed one final fast lap before complying; a tire failure at speed caused the crash. Having now lost two drivers to serious or fatal incidents, McReynolds considered leaving motorsport entirely.
After a season with Dale Jarrett in 1995 and overseeing Irvan's recovery and return in 1996, McReynolds took over as crew chief for Dale Earnhardt at Richard Childress Racing in 1997. The role placed him alongside the sport's most iconic driver.
While the 1997 season did not produce a race win, McReynolds was on the pit box for Earnhardt's historic victory in the 1998 Daytona 500 — Earnhardt's first win in the race in twenty attempts. The victory, greeted by a procession of NASCAR crew members from pit road to shake Earnhardt's hand through the driver's window, became one of the most celebrated moments in the sport's history. McReynolds and Earnhardt's partnership was subsequently reorganized, with McReynolds moving to oversee the No. 31 car driven by Mike Skinner for 1999 and 2000.
McReynolds ended his full-time crew chief career after the 2000 season and joined the inaugural NASCAR on Fox broadcast team in 2001 alongside play-by-play commentator Mike Joy and former champion Darrell Waltrip. Fox and NBC had just assumed centralized television rights for NASCAR's premier series in a six-year deal, and the 2001 Daytona 500 was the first race under the new arrangement.
McReynolds served as a color commentator in the Fox Cup Series booth from 2001 to 2015, the trio of Joy, Waltrip, and McReynolds remaining consistent across that span. From 2016 onward he shifted to the role of rules and technical analyst as Jeff Gordon joined the booth. He also covered Busch Series and Xfinity Series races during this period, served as a roving reporter on TNT's NASCAR package from 2007 to 2011, and co-hosted TNT's pre-race segments from 2012 to 2014. When TNT regained NASCAR television rights from 2025 onward, McReynolds returned to the network alongside Jeff Burton.
He co-hosts a regular show with Danielle Trotta on SiriusXM NASCAR Radio and co-authored two books: The Big Picture: My Life from Pit Road to the Broadcast Booth and How to Become a Winning Crew Chief.
McReynolds briefly served as an advisor to Petty Enterprises in 2002 and was a minority owner of the Bang! Racing team in the NASCAR Craftsman Truck Series during its single season in 2004. In 2022 he returned to the pit box at the Ag-Pro 300 for Jeffrey Earnhardt at Richard Childress Racing, recording a second-place finish and a qualifying track record. He made further crew chief appearances for Jordan Anderson in 2023 and 2024.
McReynolds was inducted into the Alabama Auto Racing Pioneers Hall of Fame in 2013. His son Brandon McReynolds is a racing driver and spotter; his daughter Kendall is married to NASCAR team owner and driver Jordan Anderson.